P1 is a student-built electric drive-by-wire vehicle owned and operated by Bucknell University. Originally built at Stanford University with funding from Nissan Motor Company, Ltd., P1 has been used for many research investigations including vehicle system diagnostics, stabilization at the limits of handling, control of high-sideslip (drift) maneuvers, lane-keeping assistance, road friction and state estimation. The actuation and instrumentation suites allow for many types of investigations with more flexibility than typically possible with instrumented production cars.
The dynamics of P1 match reasonably well with typical passenger cars or sport sedans, depending on the tire selection. The mass of the vehicle, despite the lack of body, as well as the wheelbase and track width fall within typical ranges for productin passenger vehicles. The only significant difference is that P1 has an atypically low yaw moment of inertia and a slightly larger roll moment of inertia. These atypical values are a result of the flat battery pack underneath the driver and passenger seats. Values for all of these dynamics are provide in the parameters section of this page. Experimental speeds up to approximately 30 m/s are possible given sufficient testing space.
P1 has a unique set of actuators. The car is outfitted with an electric by-wire drivetrain comprised of two separate AC induction motors, each driving one of the rear wheels. Control of the motors is done separately, allowing for different torque commands to be provided to each. As a result, experiments with varying rear wheel torques can be accomplished. Similarly, the front steering is separated left/right with servomotors driving Pittman arms to steer the wheels. The highly responsive (up to 8 Hz while in motion) steering actuators can be controlled individual to generate desired steering angles on each wheel. Force-feedback can also be applied to the steering wheel.
P1 is equipped with a Hemisphere VS330 dual-antenna GPS system that provides position, velocity, and attitude data. To supplement the data from the GPS, a custom-coded Kalman Filter is used to fuse measurements from a 6 DOF MEMS IMU with the GPS data for a state update rate of 500 Hz. Additional data is collected from wheelspeed sensors and load cells in tie rods/toe links at each wheel as well as voltage and current measurements for each actuator. A pair of Michigan Scientific LW9.5 wheel force transducers provide 6-axis tire force and moment measurements. The wheel force transducers are provided though National Science Foundation MRI Grant 1726283.
To take advantage of the capabilities of P1, Bucknell University has partnered with the Larson Transportation Institute at Penn State University to provide access to the LTI test track facility. This site features a 1-mile oval, a 400-foot handling area, and a vehicle durability-testing course.
Bucknell University is proud to operate a full-scale vehicle testbed and recognizes the challenges associated with vehicle experimentation. As a result, Bucknell invites researchers to propose research experiments that could be completed with P1 at Penn State LTI. If feasible, Bucknell and Penn State will invite researchers to join the research teams to complete the proposed experiments. A short proposal form is provided below.
A parameter set is available for P1. These parameters are best-estimates based on model fits completed over the years. Sufficient parameters are included to model the vehicle with lateral, longitudinal, yaw, roll, and four wheel speed states.P1 Parameter Script (MATLAB)
The parameters can be obtained by opening MATLAB and running the
p1_params. Upon completion, the best-estimate parameter set
will be loaded into the MATLAB environment. The parameters required for a simple
bicycle model representation of the vehicle are given in the table below.
Similarly, the suspension kinematics have been identified and are
provided in the form of lookup tables. Running
sglu = p1_sglu; from
the MATLAB function linked above will generate the lookup tables in a variable
sglu which can then be used to determine the suspension kinematics
over a range of steering angles.
|Yaw Moment of Inertia||Izz||1300||kg-m2|
|CG-Front Axle Distance||a||1.35||m|
|CG-Rear Axle Distance||b||1.1||m|
|Front Axle Cornering Stiffness||C_a_f||75000||N/rad|
|Rear Axle Cornering Stiffness||C_a_r||135000||N/rad|
P1 has been used for many different experiments over the years.
The data from experiments performed since P1 was acquired by Bucknell University
is compiled in the following section. While certain experiments focus on data
from specific sensors, each data set includes data from all sensors on the car.
The format is a MATLAB data file which loads with 5 variables. The
info variable is a structure which contains basic information about
the testing. It includes the date and location of the testing, notes entered by
the researchers who conducted the experiment, and car software version
TET variable contains debug information for the
on-board computer and is typically not needed. The
variable is another struct that describes the data. While this can change
depending on the particular test, the typical structure is described in the
table below. The
DataDescription variable is the key to unpacking
y variable, which is a matrix with a column for each signal and
a row for each time step. The columns of
y are arranged in order of
DataDescription variable. Finally, a time vector
is provided with a length matching the number of rows in
The signals in
y can be broken up into submatrices as described
DataDescription by running the script
provided below. This script also relies on the dependency
extractdata also provided below.
|Steering||12 signals||rad, rad, amps, amps, volts, volts, rad, rad, ticks, ticks, volts, volts||Contains in order: L&R motor shaft angles, L&R motor currents, L&R motor voltages, L&R gearbox shaft angles, raw L&R encoder values, and raw L&R pot values|
|INS||6||rad/s, m/s2, deg/s, m/s2, deg/s m/s2||Contains in order: Yaw rate, ax, roll rate, ay, pitch rate, & az|
|GPS||28||various||PPS, time of week, week num, Latitude, Longitude, Altitude, ECEF X, ECEF Y, ECEF Z, horizontal speed, vert velocity, course over ground, heading, roll angle, nav mode, attitude status, sats used, differential age, yaw stddev, roll stddev, horizontal rms, vertical rms, covariance N-N, covariance N-E, covariance N-U, covariance E-E, covariance E-U, covariance U-U|
|Handwheel||3||rad, rad, rad||Contains three separate handwheel angle measurements.|
|Accelerator||1||V||Contains the raw accelerator pedal signal.|
|Wheelspeeds||4||ticks/sample, ticks/sample, ticks/sample, ticks/sample||Contains wheelspeed in order data for FR, FL, RR, and RL wheels.|
|Commands||8||A, A, rad, rad, A, A, A, rad||Contains L&R steering motor current commands, L&R steering angle commands, L&R traction motor commands, & handwheel motor command, HAL command|
|SSest||21||rad, unitless, rad/s, rad/s, rad, unitless, rad/s, rad/s, m/s, m/s2, m/s, m/s2, m/s2, rad, m, m, time steps, time steps, unitless, unitless||Contains in order: 1) YAW angle, gyro sf, gyro bias, 4) rate; 5) ROLL angle, gyro sf, gyro bias, 8) rate; 9) LONGITUDINAL velocity, accel bias, 11) accel at CG; LATERAL velocity at CG, accel bias, 14) accel at CG; 15) SIDESLIP ANGLE; POSITION east (x), north (y); attitude flag, GPS delay; pos/vel flag, UPDATE pulse|
|Switches||4||bool, bool, bool, bool||Contains status of fault switch, HAL switch, cruise control switch, and brake pedal switch.|
|Load Cells||4||N, N, N, N||Contains front L&R tie rod load cell readings, rear L&R tie rod load cell readings.|
|Vehicle State||7||rad/s, rad, m/s, rad, rad/s, rad/s||Contains NON-GPS-BASED vehicle yaw rate, sideslip, horizontal speed, rear wheel speeds|
|PostProc||5||rad, rad, rad, Nm, Nm||Contains in order: left & right steer angles, ackermann angle, left & right steer torques measured by load cells|
|Tire Estimation||12||rad, rad, unitless, na, na, na, na, na, m, m, N, N||Contains in order: front slip angle, rear slip angle, tire-road friction coefficient, estimation flags, left & right pneumatic trail, left & right peak forces|
|Steering Torques||10||Nm, Nm, Nm, Nm, Nm, Nm, Nm, Nm, Nm, Nm||Contains in order: left & right aligning, Dalembert, Coulomb friction, damping, and jacking torques|
|Wheel Forces||20||N, N, N, N, N, N, Nm, Nm, Nm, Nm, Nm, Nm, RPM, RPM, deg, deg, m/s^2, m/s^2||Contains in order: left & right Fx, Fy, Fz, Mx, My, Mz, wheel rotation rate, wheel rotation angle, wheel hub ax, wheel hub ay|
Experimental data, organized by date in reverse chronological order. Open "Summary of Tests" for any given date for a summary that includes the researchers' notes from each test, the maximum speed, the peak lateral acceleration, and the total test length. Tests older than 7.18.2018 are without upgraded GPS and installed wheel force transducers.
Additional test data (with older, less accurate sensing) available by request.